Hello @Duncan35,
Feature requests can be posted in the "Host Voice" section of the site. to go there click on "Discuss" at the top of these forum pages and then select "Host Voice" from the menu.
Airbnb says that they will "consider" requests that get a sufficient number of thumbs up clicks. They don't say what "sufficient" is.
I have instant book, rent a room in my permanent residance and allow same day bookings. I see that you have check-in marked as flexible. Is it important for you that it be flexible? Would it be worth considering setting a specific check-in start time, like 1/2 an hour after you get back from work, so that you can still be flexible in communication with most guests but a bit firmer with same day check-in ones?
I know everyone's circumstances are different and one person's solution may not suit all. I have checkin from 3pm to 8pm and allow same day bookings up to 3pm. I do my damdest to make sure that the room is ready again that day by 3pm if someone checks out. not always possible of course but a great feeling when it happens and there's a same day booking.
I'd give your suggestion in Host voice a thumbs up.
You could put something like "For same day bookings guests must be flexible with check in time" in the message that's automatically sent to guests who book instantly.
Steve.